KVO stands for Key-Value Observing. It allows a controller or class to observe when a property value changes.

A protocol defines a blueprint of methods, properties, and other requirements that suit a particular task or piece of functionality. The protocol can then be adopted by a class, structure, or enumeration to provide an actual implementation of those requirements. Any type that satisfies the requirements of a protocol is said to conform to that protocol. In addition to specifying requirements that conforming types must implement, you can extend a protocol to implement some of these requirements or to implement additional functionality that conforming types can take advantage of.

Auto Layout is used to dynamically calculate the size and position of views based on constraints.

25 Essential ios

Interview Questions

An updated list of ios interview questions that will help companies hire top software developers.

What is Swift and what is Objective-C?

What is the app lifecycle in iOS?

What type of tests can you write to test your iOS application and why tests are good practice?

What are some ways of debugging in iOS?

What is an optional and what problem do optionals solve?

What is autorealease pool?

What is memory management handled on iOS?

What is the difference between a class and an object?

Is it faster to iterate through an NSArray or an NSSet?

What is the difference between implicit and explicit?

What is the difference between weak and strong?

What is the difference between category and extension in Objective-C?

What is KVO?

Design Patterns, name and explain.

What is protocol?

Which are the ways of achieving concurrency in iOS?

What is GCD and how is it used?

Explain the difference between Serial vs Concurrent

What is the difference between viewDidLoad and viewDidAppear? Which should you use to load data from a remote server to display in the view?

What is the reuseIdentifier for?

What considerations do you need when writing a UITableViewController which shows images downloaded from a remote server?

What is autolayout?

Types of notification

iOS Data Storage options

Ways to distribute iOS App

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Is it faster to iterate through an `NSArray` or an `NSSet`?

What is the difference between `viewDidLoad` and `viewDidAppear`? Which should you use to load data from a remote server to display in the view?

What is the `reuseIdentifier` for?

What considerations do you need when writing a `UITableViewController` which shows images downloaded from a remote server?